Copper particles are widely used for electronic materials such as copper wiring material and copper bonding material due to good electric conductivity and low price. More particularly, copper particles may be used for wiring and pier burying materials of a mount circuit board, part bonding materials of a mount circuit board, electrode materials of flat panel display, electronic sealed materials of resin products or the like.
Such copper particles may advantageously form a fine wiring using various methods such as screening printing, dispensing, ink-jetting and spraying due to their small diameter.
To make copper particles, there have been proposed various methods such as mechanical grinding, co-precipitation, spraying, sol-gel, and electrolysis. However, most copper particle making methods are too complicated or exhibit bad economical efficiency.
Korean Laid-open Patent Publication No. 10-2005-84099 discloses a method for reducing copper(II) precursor using a hydrazine-based reducing agent to make Cu2O particles and then reducing the Cu2O particles to make a copper particle composition. However, when Cu2O particles are made using such a strong reducing agent, the size of generated Cu2O particles is greatly increased due to rapid reduction reaction, so it is difficult to control shape and particle size of Cu2O assembly particles.
Meanwhile, copper particles exhibit a strong tendency to be oxidized into CuO in the atmosphere, and thus electric conductivity is deteriorated. In addition, in case copper particles have bad crystallinity, electric conductivity is also deteriorated since the bad crystallinity disturbs flow of electrons.